3. A bird is flying at 23 kilometers per hour (km/h) east with respect to the ground. Relative to which of the following would the bird's velocity be 0 km/h?
A.) A second bird flying at 23 km/h north relative to the ground
B.) A second bird flying at 23 km/h east relative to the ground
1
C.) A second bird flying at 23 km/h west relative to the ground
D.) A second bird flying at 23 km/h south relative to the ground

a.   mass number from atomic number

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

drying towels at the beach